Sub-seasonal Forecasting Skills Assessment and Deviation Analysis of CFSv2 for Summer Precipitation in Sichuan and Chongqing

Abstract

In this paper， the hindcast precipitation fields of the NCEP's second-generation climate prediction system （CFSv2） and the observed precipitation data of 182 meteorological stations in Sichuan and Chongqing from 2000 to 2009 were utilized.Sub-seasonal forecasting ability for summer precipitation and its anomaly in Sichuan-Chongqing region of this model was evaluated by use of Temporal Correlation Coefficient （TCC）， Anomaly Correlation Coefficient （ACC）， Root Mean Square Error （RMSE）， sign coincidence rate （SCR） and PS scores methods.Meanwhile， bias characteristics on probability density and frequency of precipitation was analyzed.The results show that the available forecast lead time for summer precipitation in Sichuan and Chongqing is about 3 pentads， which can simulate the high-value center of summer precipitation well， but the magnitude is too large.The high-value areas of forecasting skills are mainly located in the northwestern Sichuan Basin and northeastern Chongqing， and some forecasting skills are also available for the southern Panxi region and parts of the western Sichuan Plateau.The model can also better grasp the trend of abnormally less precipitation in summer in the Sichuan-Chongqing region， and the effective forecasting skill is within 2 pentads.The precipitation probability densities predicted and observed in each time period of the model are mainly concentrated in the order of magnitude below 10 mm； compared with the actual situation， the precipitation frequency of each magnitude predicted by the model is significantly higher， and with the extension of the forecast time， the deviation is greater， and the most obvious one is the light rain frequency.

Keywords

• forecasting skills assessment
• deviation analysis
• summer precipitation in sichuan-chongqing
• sub-seasonal forecast